Vessel fluid sensors may be employed for blood pressure sensing of rodents such as laboratory mice in medical studies. At present, blood pressure sensing is performed with a catheter that is connected to an external measurement equipment. The catheter is fluid filled and transfers the pressure mechanically. However, the blood pressure is quite inaccurate, since the system of the catheter adds a fluid pillar to the pressure and depends on the mouse body as well as the ambient temperature. It further forms a mechanical low pass that limits the dynamic of the signals. In addition, the mouse is tied to the external catheter tube, which causes massive stress to the mouse and thus reduces the value of the measured data. Finally the mouse often dies when the catheter is removed.
There are transponders existing that combine the catheter measurement principle with a wireless data link to avoid the external tube that hinders the mouse from normal activity. Those transponders still represent a large handicap for the mouse since the volume of the transponder is about 2 cm3 and thus occupies a volume in the small animal that impacts its normal anatomy. The measurement suffers from the same problems as the catheter since it also uses the fluid filled tube to transfer the pressure from the blood vessel to the pressure sensor inside the transponder capsule, but due to the shorter catheter length the effect should be limited. Furthermore, the battery powered RF transponder has a limited lifetime which is severely shorter than the live of the animal and it has to be explanted for refurbishing due to its high price.
It is an object to provide an implantable vessel fluid sensor providing an optimum pressure resolution and accuracy and being easy to implant.